The present invention relates generally to programmable gain amplifiers, and more particularly to switched capacitor circuit amplifiers.
Advances in analog signal processing require programmable gain amplifiers that are capable of amplifying a wide dynamic range of analog input signals. Additionally, such amplifiers are required to finely control the amount of the gain that is applied to an analog input signal. As target resolutions and operating speeds increase, power dissipation also undesirably increases. Multiple stage programmable gain amplifiers are used to achieve wide dynamic ranges. However, operational amplifiers consume a disproportionate amount of power.
The present invention is directed towards a switched capacitor programmable amplifier circuit. According to one aspect of the invention, the switched capacitor programmable amplifier circuit comprises a first, second, and third capacitor and an amplifier. The first capacitor is configured to store a sampled charge that is associated with an input signal during a sampling phase and transfer the sampled charge during a holding phase. The second capacitor is configured to discharge during the sampling phase and provide a first capacitive feedback path such that a first amplified charge is stored on the second capacitor during the holding phase. The third capacitor is configured to provide a second capacitive feedback path during the sampling phase and discharge during the holding phase. The amplifier is configured to amplify the transferred sampled charge using the first capacitive feedback path to produce the first amplified charge during the holding phase and amplify the stored first amplified charge using the second capacitive feedback path to produce a second amplified charge during the sampling phase.
According to another aspect of the invention, a method for amplifying a signal comprises storing a sampled charge that is associated with an input signal during a sampling phase on a first capacitor. The sampled charge is transferred from the first capacitor during the holding phase. A first capacitive feedback path is provided through which a first amplified charge is stored on a second capacitor during the holding phase. A second capacitive feedback path is provided during the sampling phase. The transferred sampled charge is amplified using the first capacitive feedback path to produce the first amplified charge during the holding phase. The stored first amplified charge is amplified using the second capacitive feedback path to produce a second amplified charge during the sampling phase.